Electronic component module and piezoelectric oscillator device

ABSTRACT

A quartz oscillator is constructed to achieve a better yield when being mass-produced, by providing a margin of strength for each of the substrates thereof while reducing the thickness of the quartz oscillator devices. A box-shaped circuit substrate is provided for mounting thereon circuit components having different heights from one another. The bottom plate of a recess in this circuit substrate has a level difference, and is constituted of a region where the thickness of the bottom plate is relatively larger and a region where the thickness of the bottom plate is relatively smaller. High-profile circuit components are mounted on the region where the thickness of the bottom plate is smaller, while low-profile components are mounted on the region where the thickness of the bottom plate is larger. By thus increasing the thickness of one portion of the bottom plate of the circuit substrate, the bending strength of the circuit substrate is improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electronic component modulewherein circuit components including an oscillation circuit are mountedon a circuit substrate, and the present invention also relates to apiezoelectric oscillator device including such an electronic componentmodule.

[0003] 2. Description of the Related Art

[0004] Portable telephone terminals now require miniaturization, and thequartz oscillator device for generating the reference oscillation signalused in the portable telephone terminal also requires a reduction insize and thickness. As the quartz oscillator device used in aconventional portable telephone terminal, a surface-mounting typestructure as shown in FIG. 6, has been disclosed to meet such a requestfor reduction in the size and thickness. This quartz oscillator device31 includes circuit components 33 including an oscillation circuit, atemperature compensation circuit, and other suitable components, aresurface-mounted on a box-shaped circuit substrate 32 defined by ceramicmulti-layered substrates, and wherein a quartz vibrator package 34accommodating a quartz member is stacked on the circuit substrate 32 todefine a lid.

[0005] In a quartz oscillator device as described above, in order tomeet the request for reducing thickness and size, the depth of therecess in the circuit substrate is determined in accordance with themost high-profile component in the circuit components, and the thicknessof the bottom plate is determined so as to have the minimum strengthrequired. Also, by using the ceramic material having a high strength fora circuit substrate, the thickness of the bottom plate of the circuitsubstrate is reduced, and the overall thickness of the quartz oscillatordevice is reduced.

[0006] However, although the thickness of the quartz oscillator devicecan be reduced by reducing the thickness of the bottom plate of therecess in the circuit substrate, the thinner the bottom plate of therecess in the circuit substrate becomes, the lower the strength of thecircuit substrate becomes. This causes the circuit substrate to be proneto cracking due to shock produced when circuit components are mountedthereon, or causes the circuit substrate to be prone to warping when thecircuit substrate is baked. This reduces the yield of quartz oscillatordevices when they are mass-produced.

SUMMARY OF THE INVENTION

[0007] To overcome the above-described problems, preferred embodimentsof the present invention solve the problems with the above-describedconventional art and greatly improve the yield when electronic componentmodules or piezoelectric oscillators are mass-produced, by providing amargin of strength for each of the substrates thereof while greatlyreducing the thickness of the electronic component modules.

[0008] Preferred embodiments of the present invention provide anelectronic component module including a circuit substrate, and a recessprovided in the top surface of the circuit substrate, the recess beingdefined by a plurality of regions where the thicknesses of the bottomplates thereof differ from one another, and the recess including atleast one portion where the circuit components are mounted on thecircuit substrate.

[0009] In an electronic component module in accordance with preferredembodiments of the present invention, the bottom of the recess of thecircuit substrate is defined by a plurality of regions where thethicknesses of the bottom plate thereof differ from one another. Hence,by mounting low-profile components on the region where the thickness ofthe bottom plate is larger, and by mounting high-profile circuitcomponents on the region where the thickness of the bottom plate issmaller, the region where the thickness of the bottom plate is smalleris restricted to only the region that is actually required. This permitsthe thickness of the bottom plate of the recess to be partially thick,or permits the area of the region where the thickness of the bottomplate is smaller to be greatly reduced, which results in a greatlyenhanced bending strength of the circuit substrate. Furthermore, theshock strength, and the mechanical-stress resistance in workingprocesses of the circuit substrate is greatly improved, and enables theyield of electronic component modules to be greatly increased.

[0010] A preferred embodiment of the present invention provides anelectronic component module including a plurality of recesses, eachpreferably having an insular shape on the top surface of the circuitsubstrate, and each accommodating a circuit component.

[0011] In an electronic component module in accordance with preferredembodiments of the present invention, since the recesses foraccommodating circuit components include a plurality of islands, thespace within the circuit substrate is greatly reduced, and even if thethickness of the bottom plate is decreased, the area of the portionwhere the thickness of the bottom plate is small, is greatly reduced. Asa result, the bending strength, the shock strength, and themechanical-stress resistance in working processes, of the electroniccomponent module is greatly enhanced, and thereby the yield whenelectronic component modules are mass-produced is greatly improved.

[0012] Preferably, at least one portion of the plurality of recesses hasa different depth from other recesses.

[0013] Moreover, in an electronic component module in accordance with asecond preferred embodiment of the present invention, since thethickness of the bottom plate of the recess is determined in accordancewith the height of each of the circuit components accommodated in therecess, the thickness of the bottom plate of the recess accommodating alow-profile circuit component is greatly increased. This permits thebending strength, the shock-resistance, and the mechanical-stressresistance in working processes of the circuit substrate is furtherenhanced.

[0014] Preferably, the top surfaces of the circuit components mounted inthe recess is arranged to be substantially flush with the top surface ofthe circuit substrate.

[0015] Furthermore, in an electronic component module in accordance withthe second preferred embodiment of the present invention, since the topsurfaces of the circuit components are substantially flush with the topsurface of the circuit substrate, wasted space over the circuitcomponents is eliminated, and thereby the thickness of the bottomsurface plate is greatly increased, and the overall thickness of theelectronic component module is greatly reduced. Also, when circuitcomponents are mounted face down, the top surfaces of the electrodes ofall circuit components are substantially flush with one another. Thisfacilitates the wiring of the circuit.

[0016] Other preferred embodiments of the present invention provide apiezoelectric oscillator including at least an oscillation circuitdefined by the above described electronic component module, andincluding a vibrator package accommodating a piezoelectric member, thevibrator package is stacked on the electronic component module, and thevibrator package is thereby integrated with the electronic componentmodule.

[0017] In an electronic component module in accordance with a preferredembodiment of the present invention, the thickness of the piezoelectricoscillator is greatly reduced by stacking an vibrator package on theelectronic component module in accordance with a preferred embodiment ofthe present invention, and the bending strength, the shock strength andthe mechanical-stress resistance in working processes of thepiezoelectric oscillator are greatly enhanced, which results in asubstantial improvement in the yield when the piezoelectric oscillatorsare mass-produced.

[0018] Meanwhile, the electronic component module is not limited to thecircuit substrate on which the oscillation circuit of a piezoelectricoscillator is mounted. Any circuit substrate which has a circuit definedby a plurality of circuit components provided thereon may be used.

[0019] Other features, elements, characteristics and advantages of thepresent invention will become more apparent from the detaileddescription of preferred embodiments below with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a cross sectional view showing a quartz oscillatordevice in accordance with a preferred embodiment of the presentinvention.

[0021]FIG. 2 is a perspective view illustrating a circuit substrate onwhich circuit components in the quartz oscillator device shown in FIG. 1are mounted.

[0022]FIG. 3 is a cross sectional view showing a quartz oscillatordevice in accordance with another preferred embodiment of the presentinvention.

[0023]FIG. 4 is a schematic perspective view showing the circuitsubstrate used in the quartz oscillator device shown in FIG. 3.

[0024]FIG. 5 is a enlarged view of the portion X shown in FIG. 3.

[0025]FIG. 6 is a partially broken cross sectional view showing thestructure of a conventional quartz oscillator device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026]FIG. 1 is a cross sectional view showing a temperaturecompensation type quartz oscillator device 1 in accordance with apreferred embodiment of the present invention, and FIG. 2 is aperspective view illustrating a circuit substrate (electronic componentmodule) on which circuit components are mounted. This quartz oscillatordevice 1 includes a surface-mounting type quartz vibrator package 3(hereinafter referred to as a “quartz vibrator”) which is integrallystacked on a box-shaped ceramic circuit substrate 2. By producing thequartz vibrator 3 separately from the circuit side, variations in theaccuracy of the quartz vibrator 3 are greatly reduced and the frequencyaccuracy thereof is greatly increased. Also, by integrally stacking thequartz vibrator 3 on the circuit substrate 2, the quartz vibrator 3 alsoserves as a lid for the circuit substrate 2 having a box shape. Thispermits a reduction in the number of components and enablesminiaturization of the quartz oscillator device 1.

[0027] Next, the configuration of the circuit substrate 2 will bedescribed with reference to FIG. 2. The circuit substrate 2 is definedby a ceramic multi-layer substrate including a recess 4 provided at theapproximate center thereof for mounting components, and a wall 5projected therearound. Within the recess 4, wiring patterns (not shown)are provided and defined by thick-film conductors formed by the printingand baking of a conductor paste. Connection electrodes 7 a and 7 b areprovided at the four corners on the top surface of the wall 5, and asshown in FIG. 1, external electrodes 8 are provided at the four cornerson the bottom surface. The connection electrodes 7 a and 7 b on the topsurface establish the connection with the quartz vibrator 3. Twoelectrodes 7 a among the four connection electrodes on the top surfaceestablish the connection with the terminal electrode of a quartz member14, and the other two electrodes 7 b establish the connection with ashielding plate 15 to define a ground electrode. The external electrodes8 on the bottom surface define connection electrodes used when thequartz oscillator device 1 is surface-mounted on a printed circuit boardor other suitable component. One of the four external electrodes definesa signal output, another is connected to a power-supply line, and theremaining two are connected to a ground line. Although not shown in thefigures, the connection electrodes 7 a and 7 b, the external electrodes8, and the wiring patterns are interconnected through embedded wiringand via-holes in the circuit substrate 2 having a multilayer structure.Also, metallic layers (not shown) for shielding are laminated within thecircuit substrate 2.

[0028] On the circuit substrate 2, circuit components other than thequartz vibrator 3 are provided in the circuits defining the quartzoscillator device 1, such as an oscillation circuit, a temperaturecompensation circuit, a buffer amplifier circuit, or other suitablecomponent. For this purpose, on the circuit substrate 2,surface-mounting type circuit components defining these circuits arepreferably mounted by reflow soldering. For example, within the recess4, transistors for oscillation and buffer amplification, a varicapdiode, a chip-laminated capacitor, a chip thermistor for temperaturecompensation, chip resistors, and other suitable components aresurface-mounted. On the bottom surface of the circuit substrate 2, aprinting resistor 6 is provided, and the bottom surface of the circuitsubstrate 2 is covered by an insulating film except in the regionsoccupied by the external electrodes 8.

[0029] The top surface of the bottom plate in the recess of the circuitsubstrate 2 is an uneven surface having steps. In FIG. 1, the bottom isdivided into two regions, that is, the high-profile region 9 where thethickness of the bottom plate is greater and the low-profile region 10where the thickness of the bottom plate is smaller. However, the topsurface of the bottom plate of the recess 4 may instead be provided withthree or more steps. Among the circuit components, high-profilecomponents 12 such as transistors and a diode are mounted in thelow-profile region 10, and low-profile components 11 such as achip-laminated capacitor and chip resistors are mounted in thehigh-profile region 9.

[0030] As shown in FIG. 1, when the top surface of the bottom plate ofthe recess 4 includes two steps, the circuit substrate 2 is formed bylaminating three ceramic layers including the wall 5. Herein, the bottomplate in the low-profile region 10 (i.e., the smallest plate thickness)do has the smallest plate thickness for obtaining the required strength.The thickness of the bottom plate in the high-profile regions 9 d₁ (>d₀)is set so that the level difference (d₁−d₀) substantially equals thedifference in the height between the high-profile components 12 and thelow-profile components 11, and such that the height of the wall 5 issubstantially equal to the heights of the low-profile components 11.Therefore, the top surfaces of the circuit components 11 and 12 aresubstantially flush with the top surface of the circuit substrate 2, andthereby wasted space is eliminated between the top surfaces of thecircuit components 11 and 12 and the bottom surface of the quartzvibrator 3 (Conventionally, since the thickness of the bottom plate inthe circuit substrate is reduced, unnecessary spaces are provided evenover the low-profile components).

[0031] In the regions 9 where the low-profile components 11 are mounted,since the thickness of the bottom plate has a margin of thickness by(d₁−d₀) with respect to the smallest thickness d₀, and the area of theregion 10 where the plate thickness is small is greatly reduced, andhence the bending strength of the circuit substrate 2 is greatlyenhanced without increasing the thickness of the circuit substrate 2.

[0032] Next, as illustrated in FIG. 1, the quartz member 14 isaccommodated in a case 3 having an open top surface, and is supported atboth ends thereof by the case 13. The entire top surface of the case 13is covered by a shielding plate 15, and the quartz 14 is hermeticallysealed in a package defined by the case 13 and the shielding plate 15.At the four corners of the case 13, electrodes 17 a and 17 b areprovided. Two electrodes 17 a among the four electrodes are connected tothe terminal electrode of the quartz member 14 through via-holes 16, andthe other two electrodes 17 b are conducted to the shielding plate 15through via-holes 16.

[0033] The connection electrode 7 a on the top surface of the circuitsubstrate 2 and the electrode 17 a on the bottom surface of the quartzvibrator 3 are reflow-soldered, and the connection electrode 7 b on thetop surface of the circuit substrate 2 and the electrode 17 b on thebottom surface of the quartz vibrator 3 are also reflow-soldered. Theconnection electrode 7 a and 7 b on the top surface of the circuitsubstrate 2, and the electrode 17 a and 17 b on the bottom surface ofthe quartz vibrator 3 are thereby connected together via solder 18, andthe circuit substrate 2 and the quartz vibrator 3 are mechanicallyjoined.

[0034] As described above, in this quartz oscillator device 1, thebending strength of the circuit substrate 2 is enhanced by increasingthe plate thickness at one portion of the bottom surface of the circuitsubstrate 2 and by decreasing the area of the region where the platethickness is the smallest, and hence, when circuit components aresubjected to mounting, and when thick-film printing is performed withrespect to the circuit substrate 2, the strength of the circuitsubstrate 2 during transferring is increased, and the occurrence ofcracking thereof decreased. Also, when the circuit substrate 2 isdefined by the ceramic multi-layer method wherein ceramic green sheetsare laminated and sintered, the occurrence of deformation the circuitsubstrate, such as warping or waviness is greatly reduced.

[0035] Furthermore, by disposing together a group of circuit componentshaving substantially the same height, for example, a group oflow-profile components 11 or a group of high-profile components, theunevenness of the top surface of the bottom plate in the circuitsubstrate 2 is minimized.

[0036]FIG. 3 is a cross sectional view showing a quartz oscillatordevice 21 in accordance with another preferred embodiment of the presentinvention, FIG. 4 is a perspective view showing the circuit substrate 2used in this quartz oscillator device 21, and FIG. 5 is a enlarged viewof the portion X shown in FIG. 3. As illustrated in FIG. 4, in thecircuit substrate 2 of this preferred embodiment, a plurality ofrecesses are configured into island shapes in accordance with the areaand depth of the circuit components 11 and 12 to be mounted. Whileorienting the electrodes of the circuit components upward, circuitcomponents 11 and 12 are individually accommodated face down in therecesses. On the top surface of the circuit substrate 2, wiring patterns(in FIG. 4, only one portion of wiring patterns is shown) are providedby thick-film conductors. As illustrated in FIG. 5, the wiring patterns22 and the electrode 23 of the circuit components 11 and 12 are bondedby solder 24, on the top surface of the circuit substrate 2.

[0037] In the quartz oscillator device 21 having the above-describedstructure, since the space between all circuit components 11 and 12 areeliminated and filled with the circuit substrate 2, the bending strengthof the circuit substrate 2 is significantly improved. Moreover, sincethe depths of all recesses 4 are in accordance with the heights of thecircuit components 11 and 12, the thicknesses of the bottom plate underthe low-profile components 11 is increased, and the strength of thecircuit substrate 2 is greatly enhanced. Also, since the top surfaces ofall circuit components and the top surface of the circuit substrate 2are substantially flush with one another, soldering between the wiringpatterns 22 and the electrode 23 is greatly facilitated.

[0038] In this preferred embodiment, the strength against the shock whencircuit components are mounted, the mechanical-stress resistance, andthe strength against the shock when thick-film printing is performed aregreatly enhanced, and thereby the yield of the quartz oscillator device1 is greatly improved.

[0039] The type of a quartz oscillator device used is not particularlylimited. For example, as described above, a temperature compensationquartz oscillator device (TCXO) may used, or a quartz oscillator devicewithout temperature compensation (SPXO) may be used. Alternatively, avoltage control quartz oscillator (VCXO) may also be used.

[0040] As is evident from the above-described description, in accordancewith the electronic component module of various preferred embodiments ofthe present invention, it is possible to enhance the bending strength ofthe circuit substrate, and to increase the shock strength or themechanical-stress resistance in working processes, which results in asubstantial improvement in the yield of electronic component modules.

[0041] This electronic component module can be used for, for example, apiezoelectric oscillator, and permit the bending strength or the shockstrength of the piezoelectric oscillator to be greatly improved.

[0042] While preferred embodiments of the present invention have beendescribed, it is to be understood that modifications will be apparent tothose skilled in the art without departing from the scope and spirit ofthe invention.

What is claimed is:
 1. An electronic component module comprising: acircuit substrate having circuit components mounted thereon; and arecess provided in the top surface of said circuit substrate, saidrecess including a plurality of regions where the thicknesses of bottomplates of said recess differ from one another, and said recess includingat least one portion of the circuit components mounted on said circuitsubstrate.
 2. An electronic component module as claimed in claim 1 ,wherein the top surface of each of the circuit components mounted insaid recess is substantially flush with the top surface of said circuitsubstrate.
 3. An electronic component module as claimed in claim 1 ,wherein said circuit components define a quartz vibrator package.
 4. Anelectronic component module as claimed in claim 1 , wherein said circuitsubstrate is a ceramic circuit substrate.
 5. An electronic componentmodule as claimed in claim 1 , wherein said circuit substrate is definedby a ceramic multi-layer substrate.
 6. An electronic component module asclaimed in claim 1 , wherein said circuit substrate includes a wallsurrounding said recess, and connection electrodes are provided at fourcorners on a top surface of the wall.
 7. An electronic component moduleas claimed in claim 6 , wherein said connection electrodes are arrangedto define a connection with the circuit components.
 8. An electroniccomponent module comprising: a circuit substrate; and a plurality ofrecesses, each being having an insular shape on the top surface of thecircuit substrate, and each accommodating a circuit component.
 9. Anelectronic component module as claimed in claim 8 , wherein at least oneportion of said plurality of recesses has a different depth from otherof said plurality of recesses.
 10. An electronic component module asclaimed in claim 8, wherein the top surface of each of the circuitcomponents mounted in said recess is substantially flush with the topsurface of said circuit substrate.
 11. An electronic component module asclaimed in claim 8 , wherein said circuit components define a quartzvibrator package.
 12. An electronic component module as claimed in claim8 , wherein said circuit substrate is a ceramic circuit substrate. 13.An electronic component module as claimed in claim 8 , wherein saidcircuit substrate includes a wall surrounding said recess, andconnection electrodes are provided at four corners on a top surface ofthe wall.
 14. An electronic component module as claimed in claim 13 ,wherein said connection electrodes are arranged to be connected with thecircuit components.
 15. A piezoelectric oscillator comprising: at leastone oscillation circuit including an electronic component module asclaimed in claim 1 ; and a vibrator package accommodating apiezoelectric member, said vibrator package being stacked on saidelectronic component module, and said vibrator package being integratedwith said electronic component module.
 16. A piezoelectric oscillatoraccording to claim 15 , wherein said vibrator package includes a casehaving an open top surface, said electronic component module beingsupported at both end portions thereof by said case.
 17. A piezoelectricoscillator according to claim 16 , further comprising a shielding plate,wherein the entire top surface of the case is covered by the shieldingplate, such that said electronic component module is hermetically sealedin said vibration package defined by the case and the shielding plate.18. A piezoelectric oscillator comprising: at least one oscillationcircuit including an electronic component module as claimed in claim 8 ;and a vibrator package accommodating a piezoelectric member, saidvibrator package being stacked on said electronic component module, andsaid vibrator package being integrated with said electronic componentmodule.
 19. A piezoelectric oscillator according to claim 18 , whereinsaid vibrator package includes a case having an open top surface, saidelectronic component module being supported at both end portions thereofby said case.
 20. A piezoelectric oscillator according to claim 19 ,further comprising a shielding plate, wherein the entire top surface ofthe case is covered by the shielding plate, such that said electroniccomponent module is hermetically sealed in said vibration packagedefined by the case and the shielding plate.